The influence of vitamin C on the urine dipstick tests in the clinical specimens: a multicenter study

Background Vitamin C may interfere with the results of urine dipstick tests. We investigated the incidence of urinary vitamin C and its interference with urine dipstick reagents using a vitamin C dipstick. Methods The incidence of urinary vitamin C was determined in patients and healthy individuals undergoing routine medical check‐ups. Interference tests were performed using samples with various amounts of added vitamin C. For clinical samples, we identified false‐negative dipstick glucose, hemoglobin, and leukocyte esterase results based on the urine sediment and serum glucose results. Results Vitamin C was found in the urine of 18.1% of the subjects overall, and 23.1% of those undergoing medical check‐ups. Dipstick results for glucose, leukocyte esterase, and hemoglobin differed between samples without vitamin C and with added vitamin C. When vitamin C was detected in clinical urine samples, 42.3%, 10.6%, and 8.2% of the glucose, hemoglobin, and leukocyte esterase dipstick tests were rated as false negative, respectively. Conclusions Vitamin C was frequently found in clinical urine samples, and its concentration was higher in individuals undergoing medical check‐ups. Urinary vitamin C can interfere with the urine dipstick results. This study gives useful information for predicting false‐negative rates of urine dipstick tests caused by vitamin C.